In conventional systems, to utilize L10 type FePt ordered alloy as a magnetic recording material, the exchange interaction between crystal lattices is reduced. Granularization of L10 type FePt ordered alloy is provided by adding a non-magnetic material such as SiO2 or C or the like. In general, granularization refers to creating a structure in which the FePt alloy is the main component, but the crystal grain boundaries are formed by non-magnetic material that surrounds the magnetic crystal grains made from FePt, so that the magnetic crystal grains are separated.
Also, utilizing FePt alloy having an L10 type crystal structure in a magnetic recording layer, the FePt layer has a (001) orientation. A (001) orientation can be formed by using an appropriate material in the underlayer formed below the FePt layer. For example, utilizing a MgO underlayer, the FePt layer is given a (001) orientation.
Furthermore, in some conventional systems, for ordering the FePt and forming the (001) orientation, it is necessary to perform a process of heating to 300 C or higher during film making or before and after.
In order to use FePt alloy having an L10 type crystal structure in a magnetic recording layer, it is necessary to form an MgO underlayer, and heat the FePt layer thereupon in order to order the FePt layer and provide the (001) orientation. In thermal assist recording and reproduction, in order to obtain a high SN ratio (SNR) and a narrow recording width, it is necessary to provide a heat sink layer below the MgO underlayer and to dissipate the excess hear during recording and after recording in the direction of the substrate. Preferably the heat sink layer is made from a material with a bcc structure such as Cr or the like, whose crystal orientation planes conform to those of the MgO underlayer, and that has a thermal conductivity larger than the MgO underlayer. However, if a Cr film is formed directly on the substrate or on an adhesion layer, the (110) orientation is dominant, and it is difficult to obtain the (100) orientation to conform to the MgO crystal orientation. On the other hand, if a thin oxide film such as MgO or the like is formed on the adhesion layer in order to obtain the (100) orientation of Cr on the substrate or on the adhesion layer, the (100) orientation can be obtained, but projections are formed on the Cr surface. When these surface projections are formed, the FePt layer formed on the MgO is affected, so ultimately projections are formed on the surface of the FePt layer, so the flying characteristics deteriorate significantly.
Accordingly, in conventional systems, for FePt alloy media having an L10 type crystal structure, even if a heat sink layer is formed, it is not possible to obtain a medium in which the MgO underlayer and the FePt layer have the desired crystal orientation and sufficient flying characteristics.